I observed a diurnal phase shift with my 117A system. I never investigated whether this was due to loop phase shifts with temperature or propagation, but it was likely a combination.
These phase shifts matter less if you are doing long term (multi-day) measurements, but, to be valid, your system has to maintain phase lock for the entire time. In my experience, that rarely happens in my location. Remember a 1 cycle hop is about 16-17 usecond. Phase shilt with temperature becomes a real worry if you are trying to adjust a local standard in a few hours or a day. FWIW, -John ================ > John,-"My concern with tuning the loop is that as the tuned circuit drifts > with > temperature, or other things, an extraneous phase shift will be intoduced > to the received signal. Remember, the phase of a complex pole pair tuned > circuit goes from +90 to -90 degrees as you sweepo through resonance. The > higher the Q, the steeper this effect would be." > +++++++++++++++++ > Don Lancaster addresses this concern in his article where he states: > âTune > this coil to 60 kHz with high quality polystyrene capacitors or the more > expensive > silver micas. Any other capacitor type is unsuitable. The coil Q should be > around > 25 to 40. More will cause temperature and tuning problems, less will let > in too > much noise.â > > To tell the truth, I really haven't given this much thought for the 30+ > years my loop > has been working. > > Â Â Â Â Â Â Â Â -Arthur > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
